Magnetic shunt for u-shaped meter cores



Dec. 18, 1951 J. INDERGAND 2,579,261

MAGNETIC sHUNT FOR U-sHAPED METER coRFs Filed Feb. 5, 1948 1/ 9 121/ lll f) I Z l/ C @J I NoN-MAGNET/c (BRASS) Y MLM..

` ATTORNEYS.

Patented Dec. 18, 1951 UNITED STATES PATENT OFFICE MAGNETIC SHUNT FOR U-SHAPED METER CORES Josef Indergand, Baar, Switzerland, assigner to Landis & Gyr, A. G., a corporation of Switzerland Application February 5, 1948, Serial No. 6,502 In Switzerland May 11, 1939 Section 1, Public Law 690, August 8, 1946 Patent expires May 11, 1959 2 Claims. (Cl. 171-264) 1 2 The present invention relates to new and useimportant disadvantage. As is generally known, ful improvements in induction measuring appathe shunting action depends largely on the qualratus, more particularly to watt hour meters. ity of the sheet iron employed in the shunt. Objects and advantages of the invention will 'Therefore endeavors have long been made to be set forth in part hereinafter and in part will 5 render ones self as independent as possible of the be obvious hereirom, or may be learned by pracunavoidable differences in the magnetic propertice with the invention, the same being realized ties of the dynamo sheet iron employed. Since and attained by means of the instrumentalities the sheets oi dynamo sheet iron of one lot are and combinations pointed out in the appended usually uniform among themselves in their magclairns, netic properties, it is obviously more advantageous The invention consists in the novel parts, conin the present nia-SS production to be able to structions, arrangements, combinations and immake the largest number` of shunt plates from one provements herein shown and deserihedlot of dynamo sheet metal and to use as little The accompanying drawings, referred to heredYDamO Sheet metal 3S lJOSSble fOl SllCh Shunl? in and constituting a part hereof, illustrate one D127S A further dSadVa-Dtag 0f these Shllnl? embodiment oi the invention, and together with arrangements iS 'the diiulty 0f adjusting GXaCly the description, serve to explain the princi-ples of the air gap bei/Ween the CWD D019 plate p10iCt011S the invention. An exact adjustment of this air gap is however,

Of the drawings; necessary for obtaining such a satisfactory shunt- Figure 1 is a side elevation of a typical, pre- 20 ing effect ferred and illustrative meter core embodying the The present invention has for its Object the present invention; and avoidance of the disadvantages of the above men- Figure 2 is e, top plan View of the current G01-e tioned shunt arrangement. In accordance with shownin Figure 1. the invention this result is attained by connecting As is knowny the load Curves of induction l5 the shunt plate to the two pole plates which are measuring apparatus show a negative error pronXed to the polar surfaces of the current core and duced by the current damping, which error is spaced therefrom by intercalation of non-magredueed to a Considerable extent by magnetic netic material, at the same time providing a bridge shunt arrangements, of which adnumber of forms or bar which is saturated at high loads, nonare known In one shunt arrangement, which magnetic material being likewise intercalated beis especially advantageous, both the total nuX tween the shunt plate and the pole plates. Prefand also the shunt-sd flux are each conducted erably, the shunt arrangements are so formed that through ai; least one air gan Such a shunt M the pole plates which extend considerably beyond rangement of this kind produces a Very Strong the polar surfaces of the current core at one longicompensating moment by the high magnetic retudinal side thereof each have a projection and sistance in the part of the curi-ent Core Can-ying the front faces of these projections are kept at the total luX, and requires only a minimum Such a distance apart from one another that subnumber of ampere tui-nn stantially no lines of force run between them.

A highly advantageous censtruetienal foi-m of The air gap conducting shunted lines of force a shunt arrangement of the kind above mem between the two pole plates is substantially elimitioned comprises two poie extension plates xed nated in this shunt arrangement due to the comto .the polaisurfaees 4of the Current Core with paratively great distance apart of the pole plate non-magnetic material interesleitedy the projectprojections from one another. Here the shunted ing parts 0f such pole extension plates being conlines of force are rather conducted substantially nested together by a. magnetic :bridge or bar so over the bridge or bar of the shunt plate, so that als t0 leave a narrow air gap in which is fixed a the latter, Since it has the maximum magnetic member of non megnetic material. In this arresistance, is saturated at high loads. For the rangement however, the bridgev or bar is not Shunting action Consequently only a single place saturated at high loads, but saturation takes in the System. namely the bridge 0r bar 0f the place in the two projecting parts of the pole shunt, is important. The amount of material plates by reason of the large magnetic resistance used for making JChe Shlll'lt plate Can thel'efOle be present at these places, so that a comparatively very small, so that a large number of shunt large amount of material is required for obtainplates can be made from each lot of the dynamo ing the shunting action. The mere cost of the sheet iron.

large amount of metal required is not the most The exact initial adjustment of the shunt can E be accomplished simply and easily in view of the fact that the path of the shunted lines of force between` the pole plates and the shunt plate is formed entirely of a non-metallic spacing plate which can be of any desired predetermined thickness, the thickness being chosen in accordance with the magnetic characteristics of the shunt plate and the magnitude of the error to be corrected.

It will be understood that the foregoing general description and the following detailed description as well are exemplary and explanatory of the invention but are not restrictive thereof.

Referring now in detail to the illustrative and preferred embodiment of the invention as shown in the accompanying drawings, the current core I is formed as a laminated U-shaped core of conventional form on the pole pieces of which are fixed the pole extension plates 2 and 3 which are secured theretoby screws 4 and spaced from the pole pieces by the interposed non-metallic plates I3 and lil. The pole extension plates 2 and 3 are formed of magnetizable material such as dynamo sheet iron and project beyond the pole surfaces. of the current core l, the portions of these extension plates which project towards each other being numbered 5 and 6. The adjacent and usually parallel edges 'I and 8 of the pole extension plates 2 and 3 are mechanically held in fixed relation to each other at such a to the pole extension plates 2 and 3 by means of the non-magnetic rivets II, preferably of brass, while the shunt plate 9 is accurately and rigidly spaced from the projecting portions 5 and 6 by meansl of the non-magnetic plate ID which is also preferably of brass, the thickness of the plate I D being determined by the magnetic characteristics of the particular lot of dynamo sheet iron from which the plate 9 is formed. The plate 9 is preferably centrally enlarged, and extends beneath the pole plate eX- tension pieces 2 and 3 providing an overlapping area of the plate 9 each of which is at least of as large an area as the portion of the plate 9 lying between the edges 'I and 8, While the width of the plate 9 between the edges I and 8 is substantially or almost the same as the width of the edges 'l and 8.

In order to provide for a more exact adjustment of the saturation in the shunt 9, the shunt plate 9 may be drilled with one or more small.

holes I2, these holes. serving to reduce the cross sectional area of the shunt 9 between the hole plate edges 'I and 8 so as thereby to reduce the saturation value of the shunt.

The spacing between the edges 'I and 8 of the pole extension plates 2 and 3 is relatively great compared to the thickness of the shunt plate 9, and in actual practice is several times as great, thereby causing substantially al1 of the shunted flux to pass the plate 9 rather than cross the air gap between the plate edges I and 8. Since the bridge of the shunt plate 9 lies across the gap between the edges 'I and 8, and

the plate 9 is more closely spaced to the plates 2 and 3 than the edges 'l and 8 are from each other, the shunt 9 alone will be subject to saturation at high loads, and the active field of operation ofthe shunt is thereby limited to a very small portion. The shunt 9 is of relatively small size, and only a small amount of the dynamo sheet iron from which it is made is required thereby permitting a large number of such shunts to be made from a particular lot of magnetic material.

l rEhe difiiculty of securing an accurate adjustment of the shunt is completely avoided inasmuch as the front faces or edges 'I and 8 of the pole extension pieces are rigidly held in a Xed relation to each other, and the plate 9 is fixedly spaced from the plates 2 and 3 by means of the brass spacer plate I0. After these parts have been secured together by the rivets II, the distance remains unchangeable, and the saturation limit of the shunt plate 9 can .be adjusted or changed only by drilling in it the final compensating holes I 2.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What isI claimed is:

1. In combination in an induction measuring apparatus, a U-shaped current core having at least one air gap, pole plates secured to said core at the poles of said core, a shunt plate connected to and bridging an air gap between said pole plates, non-metallic spacing elements between the pole plates and the core, and a non-magnetic spacing member between the shunt plate and pole plates at the air gap, said pole plates both extending to one side of the core and towards each other to provide an air gap between their adjacent edges, the air gap being relatively large with reference to the space provided by the non-magnetic spacing elements whereby the shunt plate is saturated at heavy current loads and substantially no lines of force run between the pole plates at the air gap.

2. A current core as claimed in claim 1 in which the shunt plate has a hole drilled therein in the air gap.

JOSEF INDERGAND.

REFERENCES CITED rIhe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,699,777 Callsen Jan. 22, 1929 1,709,773 Callsen Apr. 16, 1929 1,925,860 Barnes Sept. 5, 1933 1,996,936 Spahn Apr. 9, 1935 FOREIGN PATENTS Number Country Date 808,066 France i Nov. 6, 1936 

